2.5.3 Firing rule

The firing rule indicates under which conditions a transition may fire, and what the effect of the firing is on the marking. Depending on the net type and the time option, up to three different firing rules can be chosen:

<N> normal firing rule

According to the normal firing rule, a transition is enabled if the number of tokens on each pre-place is not less than the multiplicity of the arc of this pre-place to the transition. Firing a transition causes as many tokens to be subtracted from each pre-place as the multiplicity of the corresponding arc to the transition, and as many tokens to be added to each post-place as the multiplicity of the corresponding arc from the transition [Sta90, Definition 2.4 (25)].

Please note: Reduction is possible only under this firing rule!

<C> normal firing rule with capacities

Compared with the normal firing rule, the firability of the transitions is further restricted by upper bounds (capacities) for the number of tokens on each place. The capacity of a place may also be infinite. [Sta90, Definition 10.2 (102)].

The symbol oo signifies an infinite capacity, and is to be entered with <o> . It corresponds to a system-dependent constant.

A place which already contains more tokens at the initial marking than its capacity allows is considered overloaded (overloaded).

<S> safe firing rule

This rule can only be useded with ordinary nets (i.e., where all arcs have multiplicity 1). Applying it, a transition is enabled if all of its pre-places and none of its post-places are marked. Places which contain more than one token at the initial marking are considered overloaded.